title: Hydrogen sulfide is a partially redox-independent activator of the human jejunum Na+ channel, Nav1.5.
abstract: Hydrogen sulfide (H(2)S) is produced endogenously by L-cysteine metabolism. H(2)S modulates several ion channels with an unclear mechanism of action. A possible mechanism is through reduction-oxidation reactions attributable to the redox potential of the sulfur moiety. The aims of this study were to determine the effects of the H(2)S donor NaHS on Na(V)1.5, a voltage-dependent sodium channel expressed in the gastrointestinal tract in human jejunum smooth muscle cells and interstitial cells of Cajal, and to elucidate whether H(2)S acts on Na(V)1.5 by redox reactions. Whole cell Na(+) currents were recorded in freshly dissociated human jejunum circular myocytes and Na(V)1.5-transfected human embryonic kidney-293 cells. RT-PCR amplified mRNA for H(2)S enzymes cystathionine β-synthase and cystathionine γ-lyase from the human jejunum. NaHS increased native Na(+) peak currents and shifted the half-point (V(1/2)) of steady-state activation and inactivation by +21 ± 2 mV and +15 ± 3 mV, respectively. Similar effects were seen on the heterologously expressed Na(V)1.5 α subunit with EC(50)s in the 10(-4) to 10(-3) M range. The reducing agent dithiothreitol (DTT) mimicked in part the effects of NaHS by increasing peak current and positively shifting steady-state activation. DTT together with NaHS had an additive effect on steady-state activation but not on peak current, suggesting that the latter may be altered via reduction. Pretreatment with the Hg(2+)-conjugated oxidizer thimerosal or the alkylating agent N-ethylmaleimide inhibited or decreased NaHS induction of Na(V)1.5 peak current. These studies show that H(2)S activates the gastrointestinal Na(+) channel, and the mechanism of action of H(2)S is partially redox independent.
authors.affiliation: Enteric Neuroscience Program, Division of Gastroenterology and Hepatology, Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Strege
authors.forename: Cheryl E
authors.initials: CE
authors.lastname: Bernard
authors.forename: Robert E
authors.initials: RE
authors.lastname: Kraichely
authors.forename: Amelia
authors.initials: A
authors.lastname: Mazzone
authors.forename: Lei
authors.initials: L
authors.lastname: Sha
authors.forename: Arthur
authors.initials: A
authors.lastname: Beyder
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Gibbons
authors.forename: David R
authors.initials: DR
authors.lastname: Linden
authors.forename: Michael L
authors.initials: ML
authors.lastname: Kendrick
authors.forename: Michael G
authors.initials: MG
authors.lastname: Sarr
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Szurszewski
authors.forename: Gianrico
authors.initials: G
authors.lastname: Farrugia
mesh_terms: D000477:Alkylating Agents / Q000494:pharmacology; D003541:Cystathionine beta-Synthase / Q000378:metabolism; D003542:Cystathionine gamma-Lyase / Q000378:metabolism; D004229:Dithiothreitol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005033:Ethylmaleimide / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D006862:Hydrogen Sulfide / Q000378:metabolism*; D007583:Jejunum / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D062554:NAV1.5 Voltage-Gated Sodium Channel; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction; D018408:Patch-Clamp Techniques; D019163:Reducing Agents / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D013440:Sulfides / Q000494:pharmacology; D013849:Thimerosal / Q000494:pharmacology; D014162:Transfection
chemical_list: D000477:Alkylating Agents; D062554:NAV1.5 Voltage-Gated Sodium Channel; D016877:Oxidants; D019163:Reducing Agents; C568320:SCN5A protein, human; D015222:Sodium Channels; D013440:Sulfides; D013849:Thimerosal; D012964:Sodium; D003541:Cystathionine beta-Synthase; D003542:Cystathionine gamma-Lyase; C025451:sodium bisulfide; D005033:Ethylmaleimide; D004229:Dithiothreitol; D006862:Hydrogen Sulfide